Policy-based virtual routing and forwarding (VRF) assignment

ABSTRACT

A method for increasing resolution of virtual router assignment in a computer network. An incoming packet may be parsed to obtain its source and destination IP addresses. With the obtained IP addresses, and in some cases other information about the packet, a classification engine may perform a multi-field classification in a memory such as a TCAM (Ternary Content-Addressable Memory). The classification result may point to an action entry in an action table in a memory, e.g., an SRAM (Static random access memory). The action entry may indicate policy-based setting of the virtual router, and the VRF-ID. A virtual router is then assigned according to the VRF-ID. A group based classification in layer 3 of the present invention may avoid using a table to define segregation policies between hosts pair by pair.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority to previously filed U.S. provisional patent application Ser. No. 60/948,596, filed Jul. 9, 2007, entitled Policy-based Virtual Routing and Forwarding (VRF) Assignment. That provisional application is hereby incorporated by reference in its entirety.

BACKGROUND

1. Field of the Invention

The present invention relates generally to routers in computer networks, and more particularly to a method of increasing resolution of virtual router assignment.

2. Description of Related Art

Routers are used to forward IP traffic in computer networks. To prevent information leaks, an Internet service provider may need to segregate traffic of different customers, and an enterprise may want to segregate traffic of different groups. Virtual routing and forwarding (VRF) may be used for such traffic segregation. VRF is a technology which allows several virtual routers to exist in one Internet router and work simultaneously.

FIG. 1 illustrates a simplified example of a part of a computer network of an enterprise. The enterprise may have multiple groups, e.g., groups BLUE, RED and GREEN. As shown, the computer network may have a number of VLANs (virtual LANs), and each of the VLANs may be used for network traffic among hosts belonging to one group, e.g., a blue VLAN 101 b for the group BLUE, a red VLAN 101 r for the group RED, and a green VLAN 101 g for the group GREEN. The blue VLAN 101 b may have hosts 1 b, 2 b, 3 b and 4 b belonging to the group BLUE, the red VLAN 101 r may have hosts 1 r and 2 r belonging to the group RED, and the green VLAN 101 g may have hosts 1 g and 2 g belonging to the group GREEN. A router 102 may contain a number of virtual routers, e.g., virtual routers B, R and G. Each virtual router may be identified by a VRF-ID (a pointer to address spaces in a routing table), and may function according to its own routing table, thus separating traffic of different groups of the enterprise. The currently available technology makes VRF assignment at layer 2 of the Internet Protocol and identifies virtual routers with port, VLAN tag or MPLS (Multiprotocol Label Switching) tunnel interface of a packet.

An enterprise may want to further segregate traffic between hosts in one VLAN, and sometimes may want to allow a host in one group (or VLAN) to communicate with a host in another group (or VLAN). For example, in the computer network shown in FIG. 1, hosts 1 b and 2 b may be workstations, and hosts 3 b and 4 b may be IP phones. The enterprise may want to separate workstation traffic from IP phone traffic, separate the traffic of the group BLUE from the traffic of the group GREEN, but allow traffic between workstation hosts 1 b and 2 b in the group BLUE and hosts 1 r and 2 r in the group RED. Theoretically, the currently available technology may accomplish this by using a table to define the segregation policies between hosts pair by pair. But in practice, the table may increase greatly in size as the number of hosts in the VLANs increases. In addition, the table is not scalable and needs to be updated each time a host is added to one of the VLANs.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Embodiments of the present invention are described herein with reference to the accompanying drawings, similar reference numbers being used to indicate functionally similar elements.

FIG. 1 illustrates a simplified example of a part of a computer network employing VRF.

FIG. 2 illustrates a simplified example of a part of a computer network, in which the method of the present invention may be used.

FIG. 3 illustrates a network architecture for VRF assignment according to one embodiment of the present invention.

FIG. 4 illustrates a flow chart of a method for VRF assignment according to one embodiment of the present invention.

DETAILED DESCRIPTION

Embodiments of the present invention provide a method for increasing resolution of virtual router assignments in a computer network. In accordance with an embodiment of the present invention, a virtual router makes assignments at layer 3 of TCP/IP (Transmission Control Protocol/Internet Protocol), the network layer. An incoming packet may be parsed to obtain its source and destination IP addresses. With the obtained IP addresses, and in some cases other information about the packet, a classification engine may perform a multi-field classification in a memory such as a TCAM (Ternary Content-Addressable Memory) or other suitable memory devices. The result may point to an action entry in an action table in a memory, e.g., an SRAM (Static random access memory). The action entry may indicate policy-based setting of a virtual router, and a VRF-ID. A virtual router may be assigned according to the VRF-ID. A group based classification in layer 3 of the Internet Protocol may avoid using a table to define segregation policies between hosts pair by pair.

FIG. 2 illustrates a simplified example of a part of a computer network, in accordance with an embodiment of the present invention. Similar to the computer network shown in FIG. 1, the computer network shown in FIG. 2 may have a blue VLAN 101 b for the group BLUE, a red VLAN 101 r for the group RED, and a green VLAN 101 g for the group GREEN. The blue VLAN 101 b may have hosts 1 b, 2 b, 3 b and 4 b, wherein hosts 1 b and 2 b may be workstations, and hosts 3 b and 4 b may be IP phones, for example. The red VLAN 101 r may have hosts 1 r and 2 r, and the green VLAN 101 g may have hosts 1 g and 2 g. The enterprise may want to separate workstation hosts 1 b and 2 b from IP phone hosts 3 b and 4 b, separate workstation hosts 1 b and 2 b in the group BLUE from the group GREEN, but allow traffic between workstation hosts 1 b and 2 b in the group BLUE and hosts 1 r and 2 r in the group RED.

In contrast to the computer network shown in FIG. 1, more virtual routers may be used to separate/enable traffic among groups BLUE, RED and GREEN in the computer network shown in FIG. 2. For example, in addition to the virtual router R for the group RED and the virtual router G for the group GREEN, a virtual router B1 may be used for workstation traffic in the group BLUE, a virtual router B2 may be used for IP phone traffic in the group BLUE, and a virtual router P may be used for traffic between workstation hosts 1 b and 2 b in the group BLUE and the hosts in the group RED.

FIG. 3 illustrates a switch 300 that utilizes VRF assignment according to one embodiment of the present invention.

The present invention uses the IP address of a packet to make the VRF assignment in layer 3 of the Internet Protocol. Accordingly, a header parser 302 may parse an incoming packet from a network interface 301 to obtain its source and destination IP addresses. The header parser may also obtain other information about the packet, e.g., the packet's source and destination MAC (Media Access Control) addresses, the packet's source and destination TCP (Transmission Control Protocol) or UDP (User Datagram Protocol) ports or the VLAN tag of the VLAN the packet is from.

A classification engine 305 may be placed anywhere between the header parser 302 and a router engine 306. The classification engine 305 may receive the source and destination IP addresses of the incoming packet from the header parser 302. The classification engine 305 may send the IP addresses to a memory such as a TCAM (Ternary Content-Addressable Memory) 304 or other suitable memory devices and perform a multi-field classification in the TCAM. The TCAM may keep information about hosts in the computer network, e.g., their IP addresses, MAC addresses, VLAN tags, and TCP or UDP ports. The TCAM may also store other information about the hosts, i.e., whether a host is a workstation host or an IP phone host. In one embodiment, a CAM (Content-Addressable Memory) or other classification method such as tree or hash based classification may be used for the multi-field classification. To improve the accuracy of the classification, in addition to the IP addresses of the packets, the multi-field classification may be performed together with other information about the packet, e.g., the packet's source and destination MAC addresses, its source and destination TCP or UDP ports, or the VLAN tag of the VLAN it is from. The fields may also include, e.g., source/destination network interface or port; Layer 3 protocol; 802.1p User Priority; IP-DSCP or MPLS-EXP fields; MPLS labels and their number; and Layer 4 protocol.

The classification engine 305 may hold a database of rules and an action table containing an action entry associated with each of the rules. The rules may be stored in one memory device, such as the TCAM 303, and the action table may be stored in another memory device, e.g., an SRAM 304.

A rule is a bit string generated from various packet header fields and/or the switch information (such as a packet ingress/egress port). A rule may represent a specific packet stream or an aggregation of streams. To represent an aggregation of streams, some bits in the rule may be set as, e.g., “Don't care.” A rule for a specific stream may use exact value of all bits.

The classification engine 305 may perform a multi-field classification in the TCAM to find a rule matching the IP addresses of the incoming packet. The classification engine 305 may then access the action table in the SRAM 304 for an action entry associated with the rule. The action table may have a number of action entries. An action may instruct the switch 300 about what to do with a packet matching the rule, including but not limited to: discard/accept, forward to a specific network interface, assign VRF-ID or assign a service to the packet, such as guaranteed bandwidth, minimum delay. As a result, a VRF-ID may be assigned to the incoming packet and a virtual router may be assigned according to the VRF-ID. The router engine 306 utilizes the appropriate virtual router corresponding to the VRF-ID assigned to a packet to determine a network interface 308 via which the packet is to be transmitted, and the packet is forwarded to the network interface 308. If the classification engine 305 cannot find a matching action entry in the memory 304, the sender of the packet may be so informed. For example, when the incoming packet is a data packet from the host 1 b to the host 2 g, the host 1 b may be informed that the transaction is not allowed, since the enterprise does not allow traffic between a host in the VLAN 101 b and a host in the VLAN 101 g.

FIG. 4 illustrates a flow chart of a method for VRF assignment according to one embodiment of the present invention.

At 401, the header parser 302 may receive an incoming packet via the network interface 301.

At 402, the header parser 302 may parse the incoming packet to obtain its source and destination IP addresses. The header parser 302 may also obtain other information about the incoming packet, e.g., the packet's source and destination MAC addresses, the packet's source and destination TCP or UDP ports or the VLAN tag of the VLAN the packet is from.

From 403 to 405, the classification engine 305 may use the IP addresses of the incoming packet from the header parser 302 to perform a multi-field classification in the TCAM 303 and the SRAM 304. The multi-field classification may be performed together with other information about the packet, e.g., the packet's source and destination MAC addresses, the packet's source and destination TCP or UDP ports or the VLAN tag of the VLAN the packet is from. The result of the multi-field classification may be a VRF-ID assigned to the incoming packet.

Specifically, at 403, a search key may be generated for the incoming packet. The search key may be a bit string that includes relevant packet header fields, provided by the header parser 302 and switch information, such as the packet source port.

At 404, the search key may be matched against the rules in the TCAM 303, and the rule which is the most similar to the search key may be selected. The rule may point to an action entry in the SRAM 304.

At 405, an action entry in the SRAM 304, which is associated with the rule from the TCAM 303, may be accessed and applied to the packet. The action may be, e.g., assign VRF-ID. If the incoming packet is a data packet from the host 1 b to the host 1 r, the action requested by the incoming packet belongs to the traffic between workstation hosts in the VLAN 101 b and hosts in the VLAN 101 r, and the classification engine 401 may obtain the VRF-ID of the virtual router P.

If the incoming packet is a data packet from the host 1 b to the host 1 g, a matching action entry may not be found, since the enterprise does not allow traffic between hosts in the VLAN 101 b and hosts in the VLAN 101 g and there is no action entry for streams between hosts in the VLAN 101 b and hosts in the VLAN 101 g in the action table. Thus, no virtual router can be assigned, and the host 1 b and its user may be so informed at 406.

At 407, in one embodiment, the virtual router P may be assigned to the incoming packet. Depending on the action requested by the incoming packet and each virtual router's permitted actions, any of virtual routers B1, B2, R or G may be assigned.

Several features and aspects of the present invention have been illustrated and described in detail with reference to particular embodiments by way of example only, and not by way of limitation. Alternative implementations and various modifications to the disclosed embodiments are within the scope and contemplation of the present disclosure. Therefore, it is intended that the invention be considered as limited only by the scope of the appended claims. 

1. A network switch device for use in a computer network, the switch device comprising: a first network interface and a second network interface; a first memory that stores rules used to assign a plurality of virtual routers implemented in the network switch device, wherein the network switch device serves a plurality of organizations and the virtual routers are configured to segregate communications traffic within the network switch device of a particular organization from communications traffic within the network switch device of other organizations; a virtual router classification engine that receives at least one of a source Internet Protocol (IP) address and a destination IP address of a packet received via the first interface, and also receives additional information related to the packet, and uses the additional information and the at least one of the source IP address and the destination IP address to perform a multi-field look-up in the first memory to determine a rule based on the multi-field look-up, matching the packet, for determining one of the virtual routers for routing the packet; a second memory that stores a plurality of action entries, wherein an action entry associates a rule to an action, and wherein one of the action entries is assignment of the one virtual router for routing the packet; and a router engine configured i) to implement the plurality of virtual routers, ii) to select the one virtual router determined by the virtual router classification engine, and iii) to use the one virtual router to determine that the packet is to be forwarded to the second network interface for transmission.
 2. The network switch device of claim 1, wherein the classification engine accesses the second memory for an action entry associated with the rule matching the packet.
 3. The network switch device of claim 1, wherein the first memory is a CAM (Content-Addressable Memory).
 4. The network switch device of claim 1, wherein the first memory is a TCAM (Ternary Content-Addressable Memory).
 5. The network switch device of claim 1, wherein the second memory is an SRAM (Static random access memory).
 6. The network switch device of claim 1, wherein the classification engine performs the multi-field classification with at least one type of information selected from the group consisting of: the packet's source MAC (Media Access Control) address, the packet's destination MAC address, the packet's source TCP (Transmission Control Protocol) port, the packet's destination TCP port, the packet's source UDP (User Datagram Protocol) port, the packet's destination UDP port, and a VLAN tag of a VLAN the packet is from.
 7. The network switch device of claim 1, wherein the first memory further stores at least one type of information selected from the group consisting of: a source MAC address, a source TCP port, a source UDP port, and a VLAN tag of a VLAN.
 8. The network switch device of claim 1, wherein the virtual router classification engine uses at least i) an indication of a port of the network switch device via which the packet ingressed, and ii) the at least one of the source IP address and the destination IP address, to perform the multi-field look-up in the first memory.
 9. The network switch device of claim 1, wherein the virtual router classification engine uses the multi-field look-up in the first memory to provide a classification of the packet.
 10. The network switch device of claim 1, wherein the second memory stores the one of the action entry as assignment of a Virtual Routing and Forwarding (VRF)-ID to the packet; and wherein router engine is configured to select the one virtual router based on the VRF-ID assigned to the packet.
 11. A method for forwarding a packet in a network switch device, the method comprising: determining at least one of a source Internet Protocol (IP) address and a destination IP address of a packet received via a first network interface of the network switch device; using the at least one of the source IP address and the destination IP address and additional information related to the packet to perform a multi-field look-up in a first memory to obtain a rule based on the multi-field look-up, matching the packet, to determine one of a plurality of virtual routers implemented by the network switch device to route the packet, wherein the network switch device serves a plurality of organizations and the virtual routers are configured to segregate communications traffic within the network switch device of a particular organization from communications traffic within the network switch device of other organizations; accessing an action table in a second memory for an action associated with the rule matching the packet, wherein one of the action entries is assignment of the one virtual router for routing the packet; assigning the one virtual router to the packet according to the one action entry in the second memory; using the one virtual router to determine a second network interface of the switch device; and forwarding the packet to the second network interface for transmission.
 12. The method of claim 11, further comprising: generating a search key with the at least one of the source IP address and the destination IP address and additional information related to the packet.
 13. The method of claim 12, further comprising: using the search key to search the first memory for the rule matching the packet.
 14. The method of claim 11, further comprising obtaining at least one type of information selected from the group consisting of: the packet's source MAC (Media Access Control) address, the packet's destination MAC address, the packet's source TCP (Transmission Control Protocol) port, the packet's destination TCP port, the packet's source UDP (User Datagram Protocol) port, the packet's destination UDP port, and the VLAN tag of the VLAN the packet is from.
 15. The method of claim 11, wherein the first memory further stores at least one type of information selected from the group consisting of: a source MAC address, a source TCP port, a source UDP port, and a VLAN tag.
 16. The method of claim 11, wherein the first memory is a TCAM (Ternary Content-Addressable Memory).
 17. The method of claim 11, further comprising: informing a sender of the packet that traffic is not allowed if no matching action is found in the second memory.
 18. The method of claim 11, wherein using the at least one of the source IP address and the destination IP address and the additional information related to the packet to perform the multi-field look-up comprises using at least i) an indication of a port of the network switch device via which the packet ingressed, and ii) the at least one of the source IP address and the destination IP address, to perform the multi-field look-up in the first memory.
 19. The method of claim 11, wherein the second memory stores the one of the action entry as assignment of a Virtual Routing and Forwarding (VRF)-ID to the packet; and wherein assigning the one virtual router to the packet comprises assigning the one virtual router to the packet based on the VRF-ID assigned to the packet.
 20. A computer program product comprising a non-transitory computer-readable medium having instructions which, when executed by a processor, perform the method of claim
 11. 